(1.) Field of the Invention
The present invention relates to a reverberation sound generator for use as a warning generator for giving a warning to the driver of an automobile, for example, or particularly as a speed warning generator which can be actuated when the car speed exceeds a preset value.
(2.) Description of the Prior Art
Speed warning generators to which the present invention is directed give a warning to the driver of a car when the car speed becomes higher than a predetermined speed, such as 100 Km/hour. The speed alarm generator utilizes contacts in a speedometer and is energizable when the car speed as indicated by the speedometer exceeds a preset warning speed. The warning means in such a speed warning generator is generally required to meet the following requirements: First, it should be constructed simply and inexpensively. Second, A sound pressure great enough to transmit a warning reliably to the driver should be ensured. The third requirement is that the warning means should be of high safety for issuing a warning sound with a good tone color so as not to disturb the driver's activities while driving the car.
To satisfy the foregoing requirements, conventional warning generators are ganged with a speedometer for detecting a car speed higher than 100 Km/hour, for example, to turn intermittently on and off the contacts for producing a warning while the car speed is exceeding the preset level. The speed warning generator incorporates a mechanical chime mechanism including a plunger mechanism energizable when the contacts are closed for striking a first vibrator plate and a spring mechanism attached to the plunger mechanism and actuatable when the contacts are opened to produce a reactive force for hitting a second vibrator plate. Thus, the prior speed warning generator has employed a chime mechanism as the warning means for producing intermittent sounds. Such a mechanical chime is simple and inexpensive in construction, can produce a warning sound of sufficiently good tone color, and hence is used effectively.
However, the mechanical chime has failed to produce sounds of a sufficient sound pressure. It has been disadvantageous in that it is subjected to limitations on the location of its installation, its orientation, and the like. One way to eliminate the above difficulties with the chime mechanism would be to provide means for increasing the sound pressure, and such means would be larger vibrator plates and increase the attractive force of the plunger mechanism with which to hit the vibrator plates, that is, increase the ampere turn of the coil of the plunger. This proposal however would be limited by its size and power comsumption. Another means for overcoming the insufficient sound pressure in the mechanical chime would be to use an electromagnetic buzzer. The electromagnetic buzzer with contacts however would be unstable in tone color because of rattles due to vibrations of the car, sound changes, and other causes. Contactless buzzers would generally emit sounds of high fundamentals since the diameter of a vibrator plate could not be increased due to the size limitation. Although the contactless buzzer would be able to ensure a sufficient sound pressure, it would give the driver discomfort and hence tend to interfere with the driver's driving activities.